A view from above Spirit on Mars. This mosaic image was taken by the navigation camera on the rover and is an overhead view of the rover on the surface. The front of the rover is up, and retracted airbags are visible underneath the spacecraft.Credit: NASA/JPL-Caltech/Cornell

Today, NASA is ending its attempts to contact the Mars exploration rover Spirit, which last communicated with the agency on March 22, 2010. The cause of its silence: the Martian winter.

Spirit relies on solar energy to run heaters that keep its internal components warm. This past Martian winter was particularly sunless, and the rover most likely endured colder internal temperatures than any of its prior six years on Mars, leaving many critical components and connections susceptible to damage from the cold, according to NASA.

Spirit landed on Mars in January 2004 (its sister rover Opportunity landed a few weeks later on the opposite side of the planet) for what was supposed to be a six-month visit. It ultimately had a successful and turbulent life lasting six years. It was loaded with tools, science instruments, and systems to investigate the composition of soil and rocks, study tiny wobbles in the rotation of Mars to gain insight about the planet's core, and monitor the atmosphere. Most notably, it discovered deposits of salts and minerals such as sulfur and silica that only form in the presence of water.

Spirit survived dust storms, sand traps, and three freezing winters (each Mars years is about two Earth years). Its days as a mobile explorer ended in January 2010, when, after several months of trying to free the rover from a sand trap, NASA decided the rover would remain a stationary science platform.

But now engineers have concluded that even this final stage of Spirit's mission is over. But a new, more capable rover is already waiting in the wings: Curiosity, scheduled to launch in November, is designed to help determine whether there was—or is—life on Mars.

"However, while we no longer believe there is a realistic probability of hearing from Spirit, the Deep Space Network may occasionally listen for any faint signals when the schedule permits," said Dave Lavery, NASA's program executive for solar system exploration, in the press release.

Two panoramas of the Martian surface from Spirit captured in 2005. Credit: NASA/JPL-Caltech/Cornell

Spirit moves its robotic arm. The image was taken by a camera on the rover. Credit: NASA/JPL-Caltech/Cornell

A mosaic of images shows the soil in front of Spirit after a series of short backward drives during attempts to extricate the rover from a sand trap in January and February 2010. Credit: NASA/JPL-Caltech/Cornell University

Second test firing of Morpheus engine. Credit: Joe Bibby

Project Morpheus is making subtle, but noisy, progress at NASA. The experimental spacecraft is designed to carry cargo to the moon, an asteroid, or Mars, but the model shown here will never actually land on such surfaces. It is being used to test new technologies, such as propulsion, guidance, navigation, and control systems, and optical sensors that would allow for a safe descent and landing.

Morpheus recently conducted its first tethered flights at Johnson Space Center (JSC) in Houston (see the video below) and will be taking its first untethered flight this month, making it the first prototype spacecraft to fly at JSC since before man walked on the moon.

Morpheus is also testing a new, greener propellant, liquid oxygen and methane. The mixture is cheaper, lighter, and safer than than traditional spacecraft fuels. It can also be stored for longer periods of time in space, and the methane could perhaps even be made from ice on the moon or Mars.

The vehicle is also focused on testing safer landing technologies, specifically a system developed by NASA to detect hazards like craters or slopes in real-time. The system, called the Autonomous Landing and Hazard Avoidance Technology, uses beams of light and optical sensors to profile a landing surface.

But the project, designed and developed in less than a year, is more than a technology demonstration, it' also a cultural shift for NASA. It's a hands-on testing approach: get the technology developed quickly and efficiently and use failures to drive improvement. "Projects like Morpheus are invigorating and infectious," said Steve Altemus, director of Johnson's Engineering Directorate, in the NASA press release. "And they help us find better and cheaper ways to do things. To challenge our existing processes. To innovate."

At a time when NASA's future is filled with lots of questions and uncertainties, innovations with a clear purpose are exactly what the agency needs.

The burn zone around the pad after the second set of engine firings. Credit: Kris Kehe

Researchers at the Space Research Center in the United Kingdom have developed a concept for a Mars rover that would use nuclear power and propellant gathered from the Martian atmosphere to hop a kilometer at a time. A vehicle that hops such a distance could cover diverse areas faster than current wheeled rovers, says Hugo Williams, lead researcher for the new hopper concept.

Taking giant leaps across a planet is not a new idea. Researchers at Draper Laboratory in Cambridge, Massachusetts have developed a prototype of such a vehicle. But the recent work stands out because it would gather carbon dioxide from the Martian atmosphere, heat it up, and discharges it through a rocket nozzle to propel the vehicle. While it will take the vehicle about a week to refuel after making a hop, Williams says having its fuel source in-situ would extend its operational time and range. The hopper would also uses a nuclear-powered engine so it would not be reliant on solar panels for energy like the current generation of rovers .

Richard Ambrosi, a researcher at the Space Research Center, says that the vehicle would use a guidance, navigation, and control system already used by other spacecraft and would be mostly autonomous. The work was published Wednesday in the Proceedings of the Royal Society.